community/mumble: bump pkgrel to fix dynamic linking issue

currently on -edge, installing then trying to run mumble produces the following error:

Error relocating /usr/bin/mumble: _ZN6google8protobuf8internal17AssignDescriptorsEPFPKNS1_15DescriptorTableEvEPN4absl12lts_202301259once_flagERKNS0_8MetadataE: symbol not found

rebuilding mumble fixes this error.